Puberty begins and ceases in response to an increase and decrease in hypothalamic release of the gonadotropin releasing hormone (GnRH) which stimulates the production and release of LH (lutenizing hormone) and FSH (follicle stimulating hormone) from the anterior pituitary gland in both males and females. Sex hormones are then released from the gonads and these hormones promote the development of external genitalia until GnRH levels fall again.

The cause of the variability in GnRH levels associated with puberty is seemingly undefined although it could be of genetic origin or due to leptin levels (this is highly theorized). Please note that excessive exposure to exogenous sex hormones or hazard medications, like chemotherapy drugs, could also initiate or terminate puberty +/- the development of external genetalia.